The present invention relates to a washing machine, and in particular to a washing machine having a drum mounted on an inclined axis, and more particularly to a suspension system used in such a machine.
Washing machines are known which include a drum rotatably mounted about a horizontal axis in a fixed water tank. The water tank is supported by a number of suspension units which are vertically mounted inside the washing machine. It is common for each of the suspension units to comprise a cylindrical body portion including an annular damper and a support rod slidably provided in the body and spring biased away from the body. The cylindrical body is fixed to the casing of the washing machine, typically using rubber washers, and the support rod is fixed to the water tank. Such a suspension system supports both the static load due to the weight of the drum, water tank, water contained in the water tank and the clothes contained in the drum, and the dynamic load when the drum is rotated, since these loads are in a generally vertical plane perpendicular to the axis of rotation of the drum. The suspension system has limited resistance to forces generally parallel to the axis of rotation of the drum, however in use there are little if any such components of force.
It has been proposed to provide a washing machine with a drum which has an axis of rotation inclined to the horizontal. One such commercially available machine is the xe2x80x9cNEPTUNExe2x80x9d available from Maytag. In this machine, vertical suspension units are used in conventional washing machines are provided to support the lower rear end of the water tank, and springs connected between the top of the machine casing and the upper front end of the water tank. This combination of suspension units supports the vertical components of the static and dynamic loads, but are unable to completely prevent the forwards and backwards movement of the tank, especially during high speed rotation of the drum, for example during spinning. This means that it is necessary to have a large gap between the water tank and the washing machine cabinet to ensure that there is no contact between these parts during operation of the washing machine.
It has not been considered possible to incline the suspension units so that these lie normal to the axis of rotation of the drum since there will be a component of the static load perpendicular to the suspension unit which will cause the support rod to band or twist with respect to the cylinder. This may prevent the correct functioning of the suspension unit and cause the damper to wear rapidly.
According to the present invention, a washing machine comprises a drum mounted for rotation about an inclined axis, a first, linear, suspension unit inclined at an angle substantially normal to the axis of rotation of the drum, and a second suspension unit provided generally parallel to the axis of the rotation of the drum.
With this arrangement, the first, linear, suspension unit is at the same angle as the main dynamic load as the drum is rotated. The dynamic load is typically much higher than the static load, typically 300 kgf as opposed to a vertical static load of 60 kgf, and therefore the first, linear, suspension unit is able to support the drum against the largest forces. The second suspension unit is able to balance the component of static force normal to that supported by the first suspension unit, and is therefore able to balance the component of force which otherwise would tend to bend or twist the first suspension unit. Accordingly, the combination of the two suspension units balances the main static and dynamic loads in the washing machine, and prolongs the life of the suspension units.
This arrangement results in very little front to back, movement of the drum and allows the drum to be located in a cabinet with a very small gap between the drum and the cabinet, and therefore allows a larger drum than normal to be provided in a standard sized cabinet.
The first, linear, suspension unit preferably comprises a body portion which slidably supports a rod which is biased away from the body. In this case, a force on the rod tends to move the rod into the body, and this movement is opposed by the bias of the rod away from the body to give the required suspension effect. Such a suspension unit gives little resilience to forces in a direction transverse to the rod. In this case, the first suspension unit preferably includes an annular damper through width the support rod slides.
As the drum is inclined, it is advantageous to provide a shroud between the inclined open mouth of the drum and the vertical front opening of the cabinet. It is preferred that this shroud is substantially rigid. This is advantageous as it ensures that items cannot accidentally pass around the outside of the drum and into the cabinet, and is also of particular advantage where a removable basket is to be passed into the drum, since the rigid shroud helps support the basket as it is inserted or removed. The rigid shroud is made possible due to the twin suspension system which minimises the movement of the drum within the cabinet.
The first and second suspension units may be connected directly to a fixed water tank within which the drum is rotatably mounted. However, it is preferred that a single rotatable tank is provided which acts as both the water tank and rotatable drum, and therefore, in use, contains both the water for washing and the items to be washed. In this case, it is preferred that the rotatable drum is mounted on a chassis, and that the suspension units are connected between the cabinet of the washing machine and the chassis.
The second suspension unit may be in the form of a tension spring provided between the front of the water tank or chassis supporting the water tank and the front of the cabinet, however it is preferred that the second suspension unit is in the form of a rear thrust bearing. This is of particular advantage where a single drum forms the water tank and holds the items to be washed. In this case, the thrust bearing is preferably formed from two low friction plates, one of which is provided on the rear of the drum or chassis supporting the water tank on drum, and the other on the cabinet of the washing machine. It is advantageous for one or both of the plates to be biased, for example by a spring towards the other plate.
it is advantageous for the second suspension unit to be provided at the back of the drum as the centre of gravity of the drum, especially when this containing water and items to be washed, it towards the back of the drum. During rotation of the drum, the drum will tend to yaw about its centre of gravity, and therefore there will be more movement of the drum further from the centre of gravity then close to the centre of gravity. Therefore, it is advantageous to have the suspension unit as close to the centre of gravity as possible as there will be minimum movement between the drum and the cabinet at this point.
Preferably, the drum is mounted to rotate about an axis inclined at about 20xc2x0 to 30xc2x0 to the horizontal.